Phytotoxic potential of essential oils from temperate climate plants against the germination of selected weeds and crops

Abstract

This work aimed to assess the phytotoxic potential of 12 essential oils (EOs) collected from plants growing in natural or cultivated stands in a temperate climate, i.e., Achillea millefolium, Acorus calamus, Carum carvi, Chamomilla recutita, Foeniculum vulgare, Lavandula angustifolia, Melissa officinalis, Mentha × piperita, Salvia officinalis, Solidago canadensis, Tanacetum vulgare and Thymus vulgaris. The germination of four weed species, i.e., Amaranthus retroflexus, Avena fatua, Bromus secalinus and Centaurea cyanus, was tested against all 12 EOs, and the germination of three crops, i.e., Avena sativa, Brassica napus and Zea mays, was tested in the presence of six EOs. The influence of five doses of each EO against the germination of the tested species was assessed in a petri dish experiment. The results were analyzed using dose-response non-linear analysis, the effective dose (ED50) and multivariate analysis. As a result, four groups of EOs of contrasting phytotoxicity were distinguished. The most phytotoxic group consisted of four EOs, namely C. carvi, T. vulgaris, M. × piperita and S. officinalis. These EOs were composed mainly of oxygenated monoterpenes in a range of 64.1–93.3 %. The least phytotoxic group consisted of S. canadensis EO, composed mainly of mono- and sesquiterpene hydrocarbons (92.3 %). In addition, principal component analysis indicated that the phytotoxic effect of the EOs also depended on the sensitivity of the plant species. Crops are more tolerant than weeds to the majority of EOs. Small-seeded species, namely A. retroflexus and C. cyanus, were the most sensitive to the EOs, while the kernels of Z. mays and the seeds of A. fatua were the most tolerant.